This invention relates to an apparatus for obtaining a specified load current or voltage wave characteristic in a resonant load, and more particularly, to an arrangement wherein the bandwidth of the resonant load is narrow compared to the Forrier spectrum of said specified wave characteristic.
It is known generally that feedback may be used to aid in the production of a specified current or voltage waveshape. It is further well known that if enough loop gain can be used, the resulting voltage or current can be made to duplicate in shape a reference voltage to any specified degree of accuracy. However, due to the frequency selectivity of the internal networks of a power generator (e.g. transmitter) and the frequency selectivity of the output network between the power generator and the narrow band load (e.g. antenna), the amount of loop gain which can be employed before the overall system breaks into oscillation is severely limited. However, when the loop gain is small, so as to prevent oscillation, then the antenna current waveshape cannot be made to duplicate a reference network waveshape.